Electric Bike Buyers’ Guide
The basics of an electric bike are the same across all brands and types. A motor, powered by a battery, provides assistance to the rider as they turn the pedals up to a speed of 25km/h, when the assistance has to cut out by law. This means you can ride them without any fear of breaking a sweat or having to climb out of the saddle and walk, shamefaced, up a hill (it’s happened to the best of us).
Beyond the basics, however, there is plenty of variation in the e-bikes available today. To get a better understanding of e-bikes, please read on.
What’s the best battery position on an e-bike?
Most e-bikes opt to put the battery in the middle of the bike, just above the pedals, or on a rack on top of the rear wheel. Each option has its own advantages.
The reason to put the battery in the middle is because weight distribution is important. By putting the battery, which is a big part of the weight of an e-bike, close to the centre and low down you end up with a bike that feels a bit more natural to ride.
Putting the battery up on the rack on the rear can have advantages, in that you can have a step-through frame because the battery is right out of the way.
Who are the main motor manufacturers?
Three names crop up a lot when you look into e-bikes: Bosch, TranzX, and Shimano. Each brand produces motors that are used by many e-bike brands.
Bosch is the clear market leader at the moment. It entered the e-bike market early on and it’s famous worldwide for its electronics expertise in many fields. Shimano makes a very good unit as well. TranzX are also experts in producing integrated e-bike systems for lower cost than Bosch or Shimano. What is important to note is that each brand has a computer diagnostic capability, which is vital when servicing e-bikes. They are also known brands in the e-bike industry and offer their dealers full technical back up, and spares availability. Going on from this, it is very important consider where you purchase your e-bike from. If you buy an e-bike from the internet, or somewhere not local to you, for example, ask yourself how would you go on if there were any technical issues with it? Would you have to send it back to the seller? Some e-bikes might seem very low in price, but there is often a trade off here with regards to support when things go wrong. Buying an e-bike from a local retailer who can provide the best pre and after-sales service and back-up really makes sense.
What’s the best position for the motor on an e-bike?
Front drive motors are the cheapest and drive power through the front wheel hub. Rear hub motors put the weight at the rear and provide better traction and more stability. Central drive motors are quickly becoming the most popular system, because they make an e-bike ride much more like a regular bike and keep weight near to the bottom bracket, providing optimum stability, which is hugely important for city bikes as well as mountain bikes.
What is the difference between a speed sensor and a torque sensor on an e-bike?
On cheaper e-bikes the assistance sometimes arrives with a jerk, while more expensive models offer a smoother experience, especially at low speeds. This is more or less down to whether a speed or torque sensor is used.
Speed sensors feature on cheaper e-bikes and generally provide an‘on or off’ feel to the motor. Torque sensors are more sophisticated and make a difference to the ride quality because they provide power relative to the rider’s input, making an e-bike feel more like a regular bike and allowing for more controlled cornering and low-speed manoeuvres.
Are there any key specs to look out for in a motor and battery?
The power of the motor and the size of the battery are both important considerations when purchasing an e-bike – how many miles it’s going to cover without running out of juice. Range anxiety is a big thing with e-bikes – people don’t want to be stranded with a flat battery.
But range is a really open-ended question. There's a certain amount of power in the battery, but how heavy the bike is, how heavy the rider is, the tyre pressure, type of terrain, the power setting the rider is using, all matter. It’s like how far you get on a tank of fuel depends on how you drive your car.
Generally the battery size will tell you how much capacity you’ve got. That is the main criteria – how many watt hours (Wh) or amp hours (Ah) you have in a battery.
The overall range of an e-bike fluctuates depending on the amount of assistance you demand from it. Most will have three or four settings running, from an eco mode where you get less assistance but the maximum range available, to a top setting that provides lots of power but will normally cut the range in half. As a rough guide most systems will get 50, possibly 60 miles [80-96km].
The official stats will tend to be a little bit higher, but like the official fuel efficiency stats for cars, that’s only in the perfect scenario.
Folding e-bikes and ones designed for short commutes might also sacrifice some range for a smaller battery that weighs less.
With regards to the motor power, 250W is the usual maximum supplied on most e-bikes. This is the EU/UK maximum limit, as is the maximum assisted speed of 25km/h (15.5 mph) – above these limits the e-bike effectively becomes a moped, requiring DVLA registration, a full motorcycle helmet, and insurance. Most e-bikes sold in the UK do not require any of these added complications.
It must be pointed out that although the maximum assisted speed for an e-bike is 15.5mph, you can still make the bike go faster than this, as quick as your legs and terrain (and speed limit!) allow. The motor will not hold you back under 15.5mph.
How much maintenance does an e-bike require?
As with any rechargeable battery you’re going to have a limited number of charges and discharges before the battery stops holding capacity in the same way. It’s similar to your mobile phone or laptop – a couple of years down the line they don’t hold the charge as well. E-bikes are the same. As with any rechargeable battery you’re going to have a limited number of charges and discharges before the battery stops holding capacity in the same way.
But you can do things that will help to wring the most out of your e-bike’s battery.
Always store your e-bike battery charged. Leaving a battery over winter or storing without charge can lead to your battery entering into a deep-sleep mode, which may be impossible to recover from, and would not be covered by the manufacturer’s warranty. In the long term, this can also degrade the battery and affect its future performance potential. Always store your e-bike with at least a 60% charge and recharge every month when not in use.
Where possible, charge and store your battery in a warm environment. Batteries hate the cold and should be kept stored on the bike or indoors at a temperature of more than 5 degrees centigrade. If you charge it indoors, the battery will accept more charge. Likewise, if you fit a battery that has been kept indoors to your bike, its range will be longer and its performance superior.
However, beyond keeping an eye on the health of your battery, which might need to be replaced every few years, there isn’t any more maintenance required on an e-bike than on a regular bike, since you really shouldn’t start fiddling with the motor.
The power system on an e-bike is not user-serviceable. You plug it in, charge it up and use it like a normal bike. There’s no extra service or maintenance needs. If there are problems with the electrical components it will be taken care of by the warranty providing the battery has been cared for as per the manufacturer’s recommendations. It should be noted that the manufacturer can analyse the battery and produce a report on how often the battery has been charged, its usage pattern, and temperature.
Uses for e-bikes?
Electric bikes are an excellent way to get to the office without requiring a change of clothes while avoiding the crush and potential delays of public transport.
Leisure cycling can be quite a social activity and fitness can make a massive difference to how well a group can stick together on a ride. A lot of people go downhill happily at their own pace, but climbing is when differences in fitness really show up. E-bikes come into their own in allowing less fit members of the group to keep up.
How much do you need to spend on an e-bike?
You can get a decent commuting e-bike or folding e-bike for around £1,000, but generally you need to spend more like £1,500 to £2,000 to get a quality hybrid bike, and probably over £3,000 for a dedicated road or mountain e-bike.
If you spend extra money on an e-bike you’re likely to be rewarded with useful extra features like integrated lights powered by the battery, GPS mapping and navigation computers, or the ability to customise the assistance provided by the motor. If you opt for a full-suspension mountain e-bike, that will also increase the cost.
Another trend in more expensive e-bikes is that the frames are custom-built to integrate the battery and motor, rather than the designer adding the parts onto an existing frame.
With some of the more expensive options, on the other hand, brands are creating frames that are designed to house a custom-made battery so the whole thing is hidden, more integrated. It’s a much more expensive engineering process to do that, but it’s becoming more popular.